If you own a Bambu X1 you will certainly be familiar with its z-drive lubrication grease. 

This cover protects you from accidental contact with the grease. Just glue it to the black metal vertical truss with double sided tape. 

CAUTION: Both the cover (if printed e.g. with PLA) and/or the double sided tape may be stressed by elevated print chamber temperatures (> 50 deg C). The cover may warp or drop and obstruct the traveling path of the heatbed.

As always I include the OpenSCAD source file for you to adapt and/or improve:

• Download and install OpenSCAD from https://www.openscad.org
• Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
• Amend the parameters at the top of the file or even amend the code.
• Save your changes (/File/Save).
• Render the design (/Design/Render).
• Export the rendered design e.g. as a .stl file (/File/Export/Export as STL).
• Slice and print.

See my other designs at
https://www.thingiverse.com/thinger13/designs